1. Field of the Invention
The present invention relates to a car power source apparatus that supplies power to a motor that drives the vehicle.
2. Description of the Related Art
To increase power supplied to the motor that drives a vehicle, the car power source apparatus increases output voltage of a battery block by connecting many rechargeable batteries in series to form that battery block. This car power source apparatus is discharged to supply power to the motor when the vehicle is driven, and is charged by a generator during regenerative braking of the vehicle. Battery discharge current determines the driving torque of the motor, and battery charging current determines the braking performance of the regenerative braking system. Therefore, to increase the driving torque of the motor that accelerates the vehicle, it is necessary to increase battery discharge current. To improve regenerative braking, charging at high currents is required. As a result, batteries of the car power source apparatus are charged and discharged with high currents. To improve the safety of batteries charged and discharged with high currents, a battery housing a current interrupt device has been developed to cut-off current when internal battery pressure becomes abnormally high. (Refer to Japanese Laid-Open Patent Publication No. 2006-128104.)
The battery described above can improve safety by cutting-off current when internal pressure becomes abnormally high. However, this battery has the drawback that the current interrupt device can be damaged by vibration to cut-off current and make the battery unusable. This is because vehicle vibration can cause the electrodes to move inside the battery case putting a load on the connection region of the current interrupt device. The connection region of the current interrupt device is designed with a connection strength that results in separation and current cut-off when internal battery pressure rises abnormally. If the connection region is too strong, it will be unable to separate and cut-off current when internal pressure rises abnormally. Consequently, there are constraints on the strength of the connection region, and it has the drawback that it separates easily with vibration. In particular, for batteries installed on-board a vehicle, vehicle vibration during driving cannot be eliminated, and the current interrupt device can cut-off current due to the vehicle vibration. If the current interrupt device of a battery in a car power source apparatus cuts-off current during driving, the motor will stop suddenly and it will be impossible to maintain smooth driving. Even worse, this battery has the drawback that in a pure electric automobile, the vehicle becomes completely unable to drive.
The present invention was developed with the object of correcting the drawbacks described above. Thus, it is an important object of the present invention to provide a car power source apparatus that improves battery safety with a current interrupt device housed in each battery to cut-off current when internal battery pressure rises abnormally, while effectively preventing current interrupt device cut-off due to vehicle vibration.